Liquid crystal display and thin film transistor substrate therefor

ABSTRACT

The invention is directed to an improved flat panel liquid crystal display (LCD). In one embodiment the improved LCD includes a liquid crystal layer that completely fills a gap formed between a color filter array and a thin film transistor (TFT) array. The TFT array includes a substrate that includes one or more pixel areas. Each pixel area may be divided into at least two pixel sub-areas. Each pixel sub-area is configured to have a different electric field than its counterparts, such that mutual compensation in the sub-areas decreases distortion of a gamma curve and improves lateral visibility of the flat panel display. In one embodiment, a first pixel electrode is formed in a first of the at least two pixel sub-areas; and a second pixel electrode is formed in a second of the at least two pixel sub-areas.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. application Ser.No. 10/916,519, filed on Aug. 12, 2004, which claims priority of KoreanPatent Application No. 10-2003-0056069, filed on Aug. 13, 2003, and allthe benefits accruing therefrom under 35 U.S.C. § 119, the contents ofwhich in its entirety are herein incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to liquid crystal displays generally, andmore particularly an improved thin film transistor array panel.

A liquid crystal display (LCD) is one of the most widely used flat paneldisplays. An LCD includes two panels provided with field-generatingelectrodes and a liquid crystal (LC) layer interposed therebetween. TheLCD displays images by applying voltages to the field-generatingelectrodes to generate an electric field in the LC layer, whichdetermines orientations of LC molecules in the LC layer which adjuststhe polarization of incident light.

A conventional LCD provides a narrow viewing angle. Various techniquesfor increasing the viewing angle have been suggested. In particular, onetechnique uses a vertically aligned LC and provides cutouts orprotrusions at each field-generating electrodes. The cutouts and theprotrusions reduce the aperture ratio. Therefore, there is a need tomaximize the pixel electrode size. However, the closeness of the pixelelectrodes causes strong lateral electric fields to form between them.The lateral electric fields dishevel orientations of the LC moleculesand produce spots and light leakage. In turn, the spots and lightleakage deteriorate overall display performance.

A LCD using cutouts or protrusions offers an excellent viewing angle,over 80 degrees in any direction. However, such a LCD has poorvisibility, inferior even to a twisted nematic mode LCD. In a LCD usingcutouts, discordance of the gamma curve between the front view and sideview causes poor visibility.

For example, in a vertically aligned LCD using cutouts, the pictureplane becomes brighter and the color shifts toward white as the viewingangle increases. When this phenomenon is excessive, the picture image isdistorted because the brightness difference between gray scalesdisappears. A solution is needed that provides LCDs with improvedvisibility.

SUMMARY OF THE INVENTION

The invention is directed to an improved flat panel liquid crystaldisplay (LCD). In one embodiment the improved LCD includes a liquidcrystal layer that completely fills a gap formed between a color filterarray and a thin film transistor (TFT) array. The TFT array includes asubstrate that includes one or more pixel areas. Each pixel area may bedivided into at least two pixel sub-areas. Each pixel sub-area isconfigured to have a different electric field than its counterparts,such that mutual compensation in the sub-areas decreases distortion of agamma curve and improves lateral visibility of the flat panel display.In one embodiment, a first pixel electrode is formed in a first of theat least two pixel sub-areas; and a second pixel electrode is formed ina second of the at least two pixel sub-areas.

Additionally, the TFT array may further include one or more gate linesformed on the substrate and extending in a substantially transversedirection. One or more storage electrode lines may be spaced apart fromthe gate lines and formed on the substrate to extend in the samesubstantially transverse direction as the gate lines. In one embodiment,each of the one or more gate lines and the one or more storage electrodelines have a multi-layer structure that includes two films that havedifferent physical characteristics.

A gate insulation layer may be formed over the gate lines and thestorage electrode lines, and a plurality of ohmic contacts formed on thegate insulation layer. Additionally, a plurality of drain electrodes, aplurality of data lines, and a plurality of coupling electrodes may beformed on the plurality of ohmic contacts and the gate insulation layer.In one embodiment, each data line is bent and includes a plurality ofpairs of oblique portions and a plurality of longitudinal portions. Thefirst ends of each pair of the plurality of pairs of oblique portionsare connected to form a chevron, and the second ends of each pair of theplurality of pairs of oblique portions are connected to at least one ofthe plurality of longitudinal portions. A pair of oblique portions ofeach of the plurality of data lines may be about one to nine timeslonger than longitudinal portions.

In another embodiment, the TFT array includes a substrate that includesone or more pixel areas. Each pixel area is separated into at least twopixel sub-areas, and each of the at least two pixel sub-areas isconfigured to decrease distortion of a gamma curve and improve lateralvisibility of the LCD display. A first pixel electrode may be formed ina first of the at least two pixel sub-areas; and a second pixelelectrode may be formed in a second of the at least two pixel sub-areas.Each of the one or more pixel areas may be divided into the at least twopixel sub-areas by one or more cutouts, or by one or more protrusions,formed between the first pixel electrode and the second pixel electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a thin film transistor array panel for a LCDaccording to an embodiment of the present invention.

FIG. 2 is a top view of a common electrode panel for a LCD according toan embodiment of the present invention.

FIG. 3 is a top view of an LCD according to the embodiment shown inFIGS. 1 and 2.

FIG. 4 is a sectional view of the LCD shown in FIG. 3 taken along theline IV-IV′.

FIG. 5 is a circuit diagram of the LCD shown in FIGS. 1, 2, 3 and 4.

FIG. 6 is a top view of an LCD according to another embodiment of thepresent invention.

FIG. 7 is a top view of a thin film transistor array panel for a LCDaccording to another embodiment of the present invention.

FIG. 8 is a top view of a common electrode panel for a LCD according toanother embodiment of the present invention.

FIG. 9 is a top view of an LCD according to the embodiment shown inFIGS. 7 and 8.

FIG. 10 is a top view of an LCD according to another embodiment of thepresent invention.

FIG. 11 is a sectional view of the LCD shown in FIG. 10 taken along theline XI-XI′.

FIG. 12 is a top view of an LCD according to another embodiment of thepresent invention.

FIG. 13 is a top view of an LCD according to another embodiment of thepresent invention.

FIG. 14 is a top view of a thin film transistor array panel for a LCDaccording to another embodiment of the present invention.

FIG. 15 is a top view of a common electrode panel for a LCD according toanother embodiment of the present invention.

FIG. 16 is a top view of an LCD according to the embodiment shown inFIGS. 14 and 15.

FIG. 17 is a sectional view of the LCD shown in FIG. 10 taken along theline XVII-XVII′.

FIG. 18 is a top view of an LCD according to another embodiment of thepresent invention.

FIG. 19 is a top view of a thin film transistor array panel for a LCDaccording to another embodiment of the present invention.

FIG. 20 is a top view of a common electrode panel for a LCD according toanother embodiment of the present invention.

FIG. 21 is a top view of an LCD according to the embodiment shown inFIGS. 19 and 20.

FIG. 22 is a sectional view of the LCD shown in FIG. 21 taken along theline XXII-XXII′.

FIG. 23 is a top view of a thin film transistor array panel for a LCDaccording to another embodiment of the present invention.

FIG. 24 is a top view of a common electrode panel for a LCD according toanother embodiment of the present invention.

FIG. 25 is a top view of an LCD according to the embodiment shown inFIGS. 23 and 24.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. The present invention may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein.

In the drawings, the thickness of layers, films and regions areexaggerated for clarity. Like numerals refer to like elementsthroughout. It will be understood that when an element such as a layer,film, region or substrate is referred to as being “on” another element,it can be directly on the other element or intervening elements may alsobe present. In contrast, when an element is referred to as being“directly on” another element, there are no intervening elementspresent.

Liquid crystal displays and thin film transistor (TFT) array panels fora LCD according to embodiments of the present invention are describedbelow with reference to the accompanying drawings.

FIG. 1 is a top view of a thin film transistor array panel for a LCDaccording to an embodiment of the present invention, FIG. 2 is a topview of a common electrode panel for a LCD according to an embodiment ofthe present invention, FIG. 3 is a top view of an LCD according to theembodiment shown in FIGS. 1 and 2, and FIG. 4 is a sectional view of theLCD shown in FIG. 3 taken along the line IV-IV′.

An LCD according to an embodiment of the present invention includes aTFT array panel 100, a common electrode panel 200, and a LC layer 3interposed between the panels 100 and 200, which contains a plurality ofLC molecules that are substantially vertically aligned to surfaces ofthe panels 100 and 200.

Referring now to FIGS. 1 and 4, a plurality of gate lines 121 and aplurality of storage electrode lines 131 are formed on an insulatingsubstrate 110.

As illustratively shown in FIG. 1, the gate lines 121 extendsubstantially in a transverse direction and are separated from eachother. Each gate line 121 transmits gate signals, and may include, notonly a plurality of gate electrodes 124, but also at least one gate pad129 for connecting to an external circuit.

Like the gate lines 121, each storage electrode line 131 extendssubstantially in the transverse direction. In one embodiment, a storageelectrode line 131 substantially parallels a gate line 121.Additionally, each storage electrode line includes a plurality ofbranches that form a corresponding plurality of storage electrodes 133.In one embodiment, each storage electrode 133 includes a pair of obliqueportions that make an angle of about 45 degrees with the storage line131. Two oblique portions forming a pair make an angle about 90 degreeswith each other. In use, storage electrode lines 131 are supplied with apredetermined voltage, for example, a common voltage applied to a commonelectrode 270 formed on the other panel 200 of the LCD, as shown in FIG.4.

Referring to FIG. 1, the lateral sides of the gate lines 121 and thestorage electrode lines 131 may be tapered. If tapered, the inclinationangle of the lateral sides with respect to a surface of the substrate110 is in a range of about 30-80 degrees.

Each of the gate lines 121 and the storage electrode lines 131 may havea multi-layered structure that includes two films that have differentphysical characteristics from each other. Illustratively, each line mayinclude a lower film (not shown) and an upper film (not shown). Theupper film is preferably made of a low resistivity metal, such as, forexample Al, a metal containing Al, or an Al alloy. A low resistivitymetal is used to reduce signal delay or voltage drop in the gate lines121 and the storage electrode lines 131. On the other hand, the lowerfilm is preferably made of a material such as Cr, Mo, or a Mo alloy.However, any material that has good contact characteristics with othermaterials, for example, indium tin oxide (ITO), indium zinc oxide (IZO)or similar materials, may be used. A good exemplary combination of thelower film material and the upper film material is Cr and an Al—Ndalloy. In such a combination, Cr forms the lower film and the Al—Ndalloy forms the upper film.

Referring to FIG. 4, gate insulating layer 140 preferably made ofsilicon nitride (SiNx) may be formed on the gate lines 121 and thestorage electrode lines 131.

A plurality of semiconductor strips 151 preferably made of hydrogenatedamorphous silicon (abbreviated to “a-Si”) is formed on the gateinsulating layer 140. As illustratively shown, each semiconductor strip151 extends substantially in the longitudinal direction and has aplurality of projections 154 branched out toward the gate electrodes124. An extension 156 may be elongated from the projection 154.

Each of the semiconductor strips 151 is repeatedly bent and includes aplurality of pairs of oblique portions and a plurality of longitudinalportions. Two oblique portions making a pair are connected to each otherto form a chevron and opposite ends of the pair of oblique portions areconnected to respective longitudinal portions. In one embodiment, theoblique portions of the semiconductor strip make an angle about 45degrees with the gate lines 121, and the longitudinal portions crossover the gate electrodes 124. Illustratively, a pair of oblique portionsis about one to nine times longer than a longitudinal portion. That is,it occupies about 50-90 percent of the total length of the pair ofoblique portions and the longitudinal portion.

The extension 156 includes a drain portion extended obliquely from theprojection 154, a pair of oblique portions making an angle about 45degrees with the gate lines 121, and a connector connecting the drainportion and an end of the pair of oblique portions.

A plurality of ohmic contact strips 161 and islands 165, preferably madeof silicide or n+ hydrogenated a-Si heavily doped with n type impurity,may be formed on the semiconductor strips 151 and extensions 156 islands154. Each ohmic contact strip has a plurality of projections 163. In oneembodiment, the projections 163 and the ohmic contact islands 165 arelocated in pairs on the projections 154 of the semiconductor strips.

The edge surfaces of the semiconductor strips 151 and the ohmic contacts161, 165, and 166 are tapered, and the inclination angles of the edgesurfaces of the semiconductor strips 151 and the ohmic contacts 161,165, and 166 are preferably in a range of about 30-80 degrees.

A plurality of data lines 171, a plurality of drain electrodes 175, anda plurality of coupling electrodes 176 are formed on the ohmic contacts161, 165, and 166 and the gate insulating layer 140, respectively.Designed to transmit data voltages, the data lines 171 extendsubstantially in the longitudinal direction and intersect both the gatelines 121 and the storage electrode lines 131. Each data line 171 isbent repeatedly and include a plurality of pairs of oblique portions anda plurality of longitudinal portions. In one embodiment, each pair ofoblique portions is connected to form a chevron. The opposite ends ofeach pair of oblique portions are connected to respective longitudinalportions. The oblique portions of the data lines 171 make an angle ofabout 45 degrees with the gate lines 121, and the longitudinal portionscross over the gate electrodes 124. The length of a pair of obliqueportions is about one to nine times the length of a longitudinalportion. That is, it occupies about 50-90 percent of the total length ofthe pair of oblique portions and the longitudinal portion. When an LCDis configured in this manner, pixel areas defined by crossing of thegate line 121 and the data line 171 appear to have a bent strip shape.

As shown in FIG. 1, each data line 171 may include 179 a data pad thatis wider than the data line for contacting another layer or an externaldevice. A plurality of branches of each data line 171 may project towarddrain electrodes 175 to form a plurality of source electrodes 173. Asshown, pairs of source electrodes 173 and drain electrodes 175 areseparated from and facing each other with a gate electrode 124 therebetween. In one embodiment, the combination of a gate electrode 124, asource electrode 173, and a drain electrode 175, together with aprojection 154 of a semiconductor strip 151, forms a TFT having achannel formed in the projection 154 disposed between the sourceelectrode 173 and the drain electrode 175.

The coupling electrode 176 extends at an end of the first portion fromthe drain electrode 175 and elongates in a horizontal direction at afirst portion is bent to substantially parallel the pair of obliqueportions of the data line 171. In one embodiment, a second portion ofthe coupling electrode 176 makes an angle of about 135 degrees with thegate line 121. Similarly, a third portion of the coupling electrode 176makes an angle of about 45 degrees with the gate line 121.

Each of data lines 171, the drain electrodes 175, and the couplingelectrodes 176 may have a multi-layered structure that includes twofilms having different physical characteristics. For example, each dataline drain electrode, and coupling electrode may include a lower film(not shown) and an upper film (not shown). In one embodiment, the upperfilm is preferably made of low resistivity metal that includes, forexample, Al or an Al alloy. A low resistivity material is used to reducesignal delay or voltage drop in the data lines. On the other hand, thelower film may be preferably made of a material that has good contactcharacteristics with indium tin oxide (ITO), indium zinc oxide (IZO) orsimilar materials. Illustrative lower film materials include but are notlimited to Cr, Mo, or a Mo alloy. A good exemplary combination of alower film material and an upper film material is Cr and Al—Nd alloy. Insuch a combination, Cr forms the lower material and an Al—Nd alloyformsthe upper film.

Additionally, the lateral sides of each of the data lines 171, the drainelectrodes 175, and the coupling electrodes 176 may be tapered. Iftapered, the inclination angle of the lateral sides with respect to asurface of the substrate 110 is in the range of about 30-80 degrees.

A passivation layer 180 may be formed on the data lines 171, the drainelectrodes 175, and the coupling electrodes 176. In one embodiment, thepassivation layer 180 is preferably made of a flat photosensitiveorganic material and low dielectric insulating material having adielectric constant under 4.0. Exemplary materials used to formpassivation layer 180 include, but are not limited to a-Si:C:O anda-Si:O:F, each formed by plasma enhanced chemical vapor deposition(PECVD). Alternatively, an inorganic material such as silicon nitrideand silicon oxide may be used.

In one embodiment, passivation layer 180 includes a plurality of contactholes 181 and 182 that expose the drain electrodes 175 and the data pads179 of the data lines 171, respectively. Additionally, the passivationlayer 180 and the gate insulating layer 140 have a plurality of contactholes 183, that expose gate pads 129 of the gate lines 121.Illustratively, the sidewalls of the contact holes 181, 182, and 183 maymake an angle of about 30-85 degrees with respect to the surface of thesubstrate 110 and may also include one or more stepped portions.Depending on the embodiment, the contact holes 181, 182, and 183 mayhave various planar shapes, such as a rectangular or circular shape. Inone embodiment, the area of each contact hole 181, 182, and 183 ispreferably greater than or equal to about 0.5 mm×15 μm and not largerthan about 2 mm×60 μm.

In one embodiment, a plurality of pairs of pixel electrodes 190 a and190 b and a plurality of contact assistants 81 and 82, which arepreferably made of ITO, IZO or Cr, are formed on the passivation layer180.

Each pair of pixel electrodes 190 a and 190 b may have a shape of a bentband that follows the shape of the pixel area. The pixel electrodes 190a and 190 b are distinguished into a first pixel electrode 190 a and asecond pixel electrode 190 b respectively having cutouts 191 and 192.The first pixel electrode 190 a and the second pixel electrode 190 bhave substantially the same shape, divide a pixel area into a right areaand a left area, and respectively occupy the right area and the leftarea. Therefore, portions of the first pixel electrode 190 a maycorrespond to parallel portions of the second pixel electrode 190 b.

The first pixel electrode 190 a is physically and electrically connectedto the drain electrodes 175 through the contact hole 181. The secondpixel electrode 190 b is physically and electrically floated, butoverlaps the coupling electrode 176 to form coupling capacitances withthe first pixel electrode 190 a. As a result, the voltage of the secondpixel electrode 190 b depends on the voltage of the first pixelelectrode 190 a. With respect to the common voltage, the voltage of thesecond pixel electrode 190 b is always smaller than that of the firstpixel electrode 190 a. The coupling relationship between the first pixelelectrode 190 a and the second pixel electrode 190 b will be describedlater in detail with reference to FIG. 5.

In one embodiment, it shows that when a pixel area includes twosub-areas with somewhat different electric fields, a mutual compensationin the two subareas improves the lateral visibility of the LCD.

A plurality of contact assistants 81 and 82 may be respectivelyconnected to the gate pad 129 of the gate lines 121 and the gate pad 179of the data lines 171 through the contact holes 182 b and 183 b formedon the passivation layer 180. The pixel electrodes 190 a and 190 b andthe contact assistants 81 and 82 may be made of ITO (indium tin oxide),IZO (indium zinc oxide), or similar materials.

The common electrode panel 200 is now described with reference to FIGS.2, 4, and 5.

Referring to FIG. 2, a black matrix 220 for preventing light leakage isformed on an insulating substrate 210 such as transparent glass. Aplurality of red, green and blue color filters 230 are formed on theblack matrix and the substrate 210 and extend substantially along thecolumns of the pixel areas and periodically bend as the shape of thepixel areas bends. In other words, the color filters 230 extendsubstantially in the longitudinal direction along pixel columns definedby black matrix 220 and are periodically bent along the shape of pixelarea. As shown in FIG. 4, an overcoat 250 is formed on the color filters230 and the black matrix 220. A common electrode 270, preferably made oftransparent conductive material such as ITO and IZO, may be formed onthe overcoat 250. In one embodiment, the common electrode 270 includes aplurality of cutouts 271 and 272. The cutouts 271 and 272 may functionas domain control means and are preferably about 9˜12 μm wide. Whenorganic protrusions replace the cutouts 271, the organic protrusions arepreferably about 5˜10 μm wide.

As shown in FIG. 4, each pair of cutouts 271 and 272 are disposed in apixel area and is bent along the shape of pixel area. The cutouts 271and 272 are respectively disposed to divide the first pixel electrodes190 a and the second pixel electrode 190 b into right half portions andleft half portions. Both ends of the cutouts 271 and 272 are bent andextend to a predetermined length in a direction that substantiallyparallels the gate lines 121. Centers of the cutouts 271 and 272 alsoextend to a predetermined length and are substantially parallel the gatelines 121. In one embodiment, the extending direction of the centers ofthe cutouts 271 and 272 is opposite to that of the ends of the cutouts271 and 272.

The LCD includes a TFT array panel 100, a color filter array panel 200facing the TFT array panel 100 and separated by a predetermined gap, anda liquid crystal layer 3 filled in the predetermined gap.

The LC molecules in the LC layer 3 are aligned such that their long axesare substantially vertical to the surfaces of the panels 100 and 200when there is no electric field. The liquid crystal layer 3 has negativedielectric anisotropy.

The thin film transistor array panel 100 and the color filter arraypanel 200 are assembled such that the pixel electrodes 190 a and 190 bprecisely correspond to the color filter 230. When the two panels 100and 200 are assembled, pixel areas are divided into a plurality ofsub-areas by the edge of the first and second pixel electrode 190 a and190 b and the cutouts 271 and 272. A liquid crystal region on eachsub-area is called a domain. Thus, in one embodiment, a pixel region isdivided into 4 domains by the cutouts 271 and 272. The domains have twoparallel longest edges. The distance between two longest edges of eachdomain, e.g., the width of the domain, is preferably about 10˜30 μm.

A pair of polarizers 12 and 22 is provided on the outer surfaces of thepanels 100 and 200, respectively, such that the transmissive axis ofeach polarizer is crossed. Additionally the pair of polarizers ispositioned so that at least one of the transmissive axes substantiallyparallels the gate lines 121.

The LCD may further include at least one retardation film (e.g., anoptical element that produces, for example, full, half, or quarter wavephase changes of polarized light). The retardation film functions tocompensate for the retardation of light caused by the LC layer 3.

In use, a common voltage is applied to the common electrode 270 and adata voltage is applied to the pixel electrodes 191 a and 191 b. Theapplication of these voltages generates a primary electric field whichis substantially perpendicular to the surfaces of the panels 100 and200. In response to the electric field, the LC molecules rotate untiltheir long axes are substantially perpendicular to the field direction.

The cutouts 271 and 272 of the common electrode 270 and the edges of thepixel electrodes 190 a and 190 b distort the primary electric field andgive it a horizontal component which determines the tilt directions ofthe LC molecules. The horizontal component of the primary electric fieldadopts four different orientations, thereby forming four domains in theLC layer 3 with different LC molecule tilt directions. The horizontalcomponent is substantially perpendicular to the first and second edgesof the cutouts 271 and 272, and substantially perpendicular to the edgeof the pixel electrode 190 a and 190 b. Accordingly, four domains havingdifferent tilt directions are formed in the LC layer 300. In analternative embodiment, a plurality of protrusions formed on the commonelectrode 270 may be substituted for the cutouts 271 and 272 because thetilt directions of the LC molecules also can be controlled by aplurality of protrusions (not shown).

The direction of a secondary electric field due to the voltagedifference between the pixel electrodes 190 a and 190 b is substantiallyperpendicular to each of the edges of the cutouts 271 and 272.Accordingly, the field direction of the secondary electric fieldcoincides with that of the horizontal component of the primary electricfield. Consequently, the secondary electric field between the pixelelectrodes 190 a and 190 b enhances the tilt directions of the LCmolecules.

Since the LCD performs inversion (i.e., inverting the polarity of anapplied voltage) such as dot inversion, column inversion, etc., asecondary electric field that enhances the tilt directions of the LCmolecules may be attained by supplying an adjacent pixel electrode witha data voltage having opposite polarity with respect to the commonvoltage. As a result, a direction of the secondary electric fieldgenerated between adjacent pixel electrodes is equivalent to thehorizontal component of the primary electric field generated between thecommon and pixel electrodes. Thus, a secondary electric field betweenthe adjacent pixel electrodes may be generated to enhance the stabilityof the domains.

In one embodiment, the tilt directions of all the domains form an angleof about 45 degrees with the gate lines 121, and the gate lines 121 areparallel to or perpendicular to the edges of the panels 100 and 200.Since a 45-degree intersection of the tilt directions and transmissiveaxes of the polarizers results in maximum transmittance, the polarizerscan be attached such that the transmissive axes of the polarizers areparallel or perpendicular to the edges of the panels 100 and 200,thereby reducing the production cost.

It should be noted that increased resistance of the data lines 171 dueto their bent structure can be compensated for by widening the datalines 171. Further, distortion of the electric field and increase of theparasitic capacitance due to increases in width of the data lines 171can, in turn, be compensated for by increasing the size of the pixelelectrodes 190 a and 190 b and by adapting a thick organic passivationlayer.

In an embodiment of the present invention, the first pixel electrode 190a is supplied with an image data voltage through the TFT. However, thevoltage of the second pixel electrode 190 b varies depending on thevoltage of the first pixel electrode 190 a, because the second pixelelectrode 190 b is capacitively coupled with the first pixel electrode190 a. Therefore, the voltage of the second pixel electrode 190 b withreference to the common voltage is always smaller than that of the firstpixel electrode 190 a.

As described above, when two pixel electrodes 190 a and 190 b havingdifferent voltages are disposed in a pixel area, the distortion of thegamma curve decreases by compensation of the two pixel electrodes 190 aand 190 b.

The reason that the voltage of the second pixel electrode 190 b withreference to the common voltage will almost always be smaller than thatof the first pixel electrode 190 a will be described with reference toFIG. 5, which is a circuit diagram of the LCD shown in FIGS. 1, 2, 3 and4.

In FIG. 5, the abbreviation “Clca”, stands for liquid crystal (LC)capacitance formed between the first pixel electrode 190 a and thecommon electrode 270; and “Cst” stands for storage capacitance formedbetween the first pixel electrode 190 a and the storage line 131. “Clcb”stands for liquid crystal (LC) capacitance formed between the secondpixel electrode 190 b and the common electrode 270 and Ccp stands forcoupling capacitance formed between the first pixel electrode 190 a andthe second pixel electrode 190 b.

The voltage Vb of the second pixel electrode 190 b with reference to thecommon voltage and the voltage Va of the first pixel electrode 190 awith reference to the common voltage are related by the voltagedistribution law as follows:Vb=Va×[Ccp/(Ccp+Clcb)].

Since, Ccp/(Ccp+Clcb) is always smaller than 1, Vb is always smallerthan Va. Persons skilled in the art will appreciate that the capacitanceCcp can be adjusted by overlapping area or distance between the secondpixel electrode 190 b and the coupling electrode 176. The overlappingarea between the second pixel electrode 190 b and the coupling electrode176 can be easily adjusted by changing width of the coupling electrode176. The distance between the second pixel electrode 190 b and thecoupling electrode 176 can be easily adjusted by changing the locationof the coupling electrode 176. For example, in one embodiment of theinvention, the coupling electrode 176 is formed on the same layer withthe data line 171. In another embodiment, the coupling electrode 176 isformed on the same layer with the gate line 121. By making this change,the distance between the second pixel electrode 190 b and the couplingelectrode 176 is increased.

Depending on the embodiment the shape of coupling electrode 176 may bechanged to have various forms. One example of such change will bedescribed in the following description. Description of the followingembodiment will focus on the distinguishing features from the embodimentof FIGS. 1 to 4. In order not to unnecessarily complicate, invention,the description of features previously described with reference to FIGS.1-4 is omitted.

FIG. 6 is a top view of an LCD according to another embodiment of thepresent invention. Compared with the embodiment of FIGS. 1 to 4, thatthe embodiment of FIG. 6 exchanged the first pixel electrode 190 a withthe second pixel electrode 190 b, and the site of the coupling electrode176 with that of the storage electrode 133. That is, the first pixelelectrode 190 a and the storage electrode 133 are disposed on left sideof a pixel area and the second electrode 190 b and the couplingelectrode 176 are disposed on right side of a pixel electrode.

Persons skilled in the art will appreciate that when a length ratio ofthe oblique portion and the longitudinal portion changes, the shape of apixel area also changes. One example of this is described in FIGS. 7-9.

FIG. 7 is a top view of a thin film transistor array panel for a LCDaccording to another embodiment of the present invention. FIG. 8 is atop view of a common electrode panel for a LCD according to anotherembodiment of the present invention. FIG. 9 is a top view of an LCDaccording to the embodiment shown in FIGS. 7 and 8.

In the embodiment of FIGS. 7 to 9, the data line 171 has enlargedlongitudinal portions. Consequently, a pixel area includes a bent bandportion and two rectangular portions that are respectively connected toboth ends of the bent band portion. In one embodiment, it is preferablethat the total length of the rectangular portions is longer than that ofthe bent band portion.

The shapes of the pixel electrodes 190 a and 190 b are formed to use allor substantially all the area of a pixel. For example, the first pixelelectrode 190 a may have two short edges that are substantially parallelthe data line 171. The second pixel electrode 190 b may have two shortedges that are substantially parallel and adjacent the gate line 121.Additionally, the second pixel electrode 190 b may have two enlarged endportions that fill all or substantially all of the pixel area.

The storage electrode 133 and the coupling electrode 176 may berespectively disposed to correspond with the center line of the firstand second electrodes 190 a and 190 b. The common electrode 270 may havecutouts 271 and 272 that respectively correspond to coupling electrode176 and storage electrode 133. As illustrated, both ends of the cutout271 may be bent and extend to a predetermined length in a directionsubstantially parallel the gate line 121. Similarly, both ends of thecutout 272 may be bent and extend to a predetermined length in adirection substantially parallel with the data line 171. The centers ofthe cutouts 271 and 272 may also extend to a predetermined length and besubstantially parallel the gate lines 121. As illustratively shown, theextending direction of the centers of the cutouts 271 and 272 may beopposite to that of the ends of the cutout 271.

The embodiment illustratively shown in FIGS. 7 to 9 diminishes thebroken display of characters formerly caused by pixel areas havingconventional bent band shapes.

In the embodiments described above, the semiconductor strips 151 havesubstantially the same planar shape as the data lines 171, the drainelectrodes 175, and the coupling electrodes 176 as well as theunderlying ohmic contacts 161, 165, and 166, except for the projections154 where TFTs are provided. For example, the projections 154 includesome exposed portions, which are not covered with the data lines 171 andthe drain electrodes 175. Illustratively, such as portions may belocated between the source electrodes 173 and the drain electrodes 175.

The structure shown in FIGS. 7 to 9 may be formed by a photo-etchingprocess that uses a photoresist of varying thickness to form theintrinsic semiconductor 151, 155, and 156, the ohmic contacts 161, 165,and 166, and the layer of data lines 171.

In one embodiment, the thin film transistor array panels of thedescribed embodiments may be manufactured using four photo-maskprocesses. A first photo-mask is used to pattern gate lines and storageelectrode lines. A second photo-mask is used to pattern the intrinsicsemiconductor layer, the ohmic contact layer, and the data line layer(after depositing the gate insulating layer, intrinsic semiconductorlayer, ohmic contact layer, and data metal layer). A third photo-mask isused to form one or more contact holes in the passivation layer. Afourth photo-mask is used to form pixel electrodes and contactassistants. Illustratively, the second photo-mask may include lighttransmissive portions, light blocking portions, and half-transmissiveportions that are disposed on channel portions of TFTs during theexposure.

The four photo-mask processes are described in detail in U.S. Pat. Nos.6,335,276 and 6,531,392, which is hereby incorporated by reference inits entirety.

FIG. 10 is a top view of an LCD according to another embodiment of thepresent invention. FIG. 11 is a sectional view of the LCD shown in FIG.10 taken along the line XI-XI.

The embodiment illustratively shown in FIGS. 10 and 11 is distinguishedfrom the embodiment of FIGS. 1 to 4 by the shapes of semiconductorstrips 151, ohmic contacts 161 and 165, and data lines 171, drainelectrodes 175, and coupling electrode 176. In the embodiment of FIGS.10 and 11, the planar pattern of the data lines 171, drain electrodes175, and coupling electrode 176 does not accord with that of thesemiconductor strips 151 and ohmic contacts 161 and 165. For example, asshown in FIGS. 10 and 11, a width of the semiconductor strips 151 and awidth of the ohmic contact strips 161 under the data lines 171 isnarrower than that of the data lines 171. In this embodiment, nosemiconductor and ohmic contacts, are formed under the couplingelectrodes 176.

Such a structure may be formed using the following exemplary processes.For example, the semiconductor strips 151 and the ohmic contacts 161 and165 may be formed by a photo-etching process. Thereafter, the data lines171, drain electrodes 175, and coupling electrodes 176 may be formed byanother photo-etching process. Illustratively, the structuraldifferences between the embodiment of FIGS. 1 to 4 and the embodiment ofFIGS. 10 and 11 arises from the difference of number of photo-etchingprocess as used to pattern the semiconductor layer, the ohmic contactlayer, and the data line layer, respectively.

FIG. 12 is a top view of a LCD according to another embodiment of theinvention. The embodiment of FIG. 12 is distinguished from theembodiment of FIG. 6 by shapes of semiconductor strips 151, ohmiccontacts 161 and 165, and data lines 171, drain electrodes 175, andcoupling electrode 176. In the embodiment of FIG. 12, the planar patternof the data lines 171, drain electrodes 175, and coupling electrode 176does not accord with that of the semiconductor strips 151 and ohmiccontacts 161 and 165. For example, a width of the semiconductor strips151 and the width of the ohmic contact strips 161 under the data lines171 is narrower than that of the data lines 171. As shown, there are nosemiconductor and ohmic contacts under the coupling electrodes 176.

The structural differences between the embodiment of FIG. 12 and theembodiment of FIG. 6 comes from the different number of photo-maskprocess as used to pattern the semiconductor layer, the ohmic contactlayer, and the data line layer. In manufacturing the embodiment of FIG.6, the semiconductor layer, the ohmic contact layer, and the data linelayer are formed using one photo-mask process, but in manufacturing theembodiment of FIG. 12, they are formed using two photo-mask processes.

FIG. 13 is a top view of an LCD according to another embodiment of thepresent invention. The embodiment of FIG. 13 is distinguished from theembodiment of FIGS. 7 to 9 by shapes of semiconductor strips 151, ohmiccontacts 161 and 165, and data lines 171, drain electrodes 175, andcoupling electrode 176. In the embodiment of FIG. 13, the planar patternof the data lines 171, drain electrodes 175, and coupling electrode 176does not accord with that of the semiconductor strips 151 and ohmiccontacts 161 and 165.

In the embodiment of FIG. 13, a width of the semiconductor strips 151and n ohmic contact strips 161 under the data lines 171 is narrower thanthat of the data lines 171. As shown, there are no semiconductor andohmic contacts under the coupling electrodes 176

The structural difference between the embodiment of FIG. 13 and theembodiment of FIGS. 7 to 9 comes from the difference of number ofphoto-mask processes used to pattern the semiconductor layer, the ohmiccontact layer, and the data line layer. In manufacturing the embodimentof FIGS. 7 to 9, the semiconductor layer, the ohmic contact layer, andthe data line layer are formed using one photo-mask process, but inmanufacturing the embodiment of FIG. 13, they are formed using twophoto-mask processes.

In the present invention, arrangement of the first pixel electrode 190 aand the second pixel electrode 190 b may be modified in various ways.Examples of such modifications are described below.

FIG. 14 is a top view of a thin film transistor array panel for a LCDaccording to another embodiment of the invention. FIG. 15 is a top viewof a common electrode panel for a LCD according to another embodiment ofthe invention. FIG. 16 is a top view of an LCD according to theembodiment shown in FIGS. 14 and 15.

A LCD according to the embodiment illustratively shown in FIGS. 14 to 17includes a TFT array panel 100, a common electrode panel 200, and a LClayer 3 interposed between the panels 100 and 200 and containing aplurality of LC molecules aligned vertical to surfaces of the panels 100and 200.

The TFT array panel 100 is now described in detail with reference toFIGS. 14, 16, and 17.

For example, a plurality of gate lines 121 and a plurality of storageelectrode lines 131 are formed on an insulating substrate 110.

The gate lines 121 extend substantially in a transverse direction andare separated from each other and transmit gate signals. The gate line121 has a plurality of gate electrodes 124 and gate pads 129 forconnecting to external circuit.

Each storage electrode line 131 extends substantially in the transversedirection and includes a plurality of expansion forming storageelectrodes 133. Illustratively, the storage electrodes 133 have a shapeof parallelogram.

Each of the gate lines 121 and the storage electrode lines 131 may havea multi-layered structure that includes two films that have differentphysical characteristics from each other. Illustratively, each line mayinclude a lower film (not shown) and an upper film (not shown). Theupper film is preferably made of a low resistivity metal, such as, forexample Al, a metal containing Al, or an Al alloy. A low resistivitymetal is used to reduce signal delay or voltage drop in the gate lines121 and the storage electrode lines 131. On the other hand, the lowerfilm is preferably made of a material such as Cr, Mo, or a Mo alloy.However, any material that has good contact characteristics with indiumtin oxide (ITO), indium zinc oxide (IZO) or similar materials may beused. A good exemplary combination of the lower film material and theupper film material is Cr and Al—Nd alloy. In such a combination, Crforms the lower film and the Al—Nd alloy forms the upper film.

Referring to FIG. 14, the lateral sides of the gate lines 121 and thestorage electrode lines 131 may be tapered. It tapered, the inclinationangle of the lateral sides with respect to a surface of the substrate110 is in a range of about 30-80 degrees.

Referring to FIG. 17, gate insulating layer 140 preferably made ofsilicon nitride (SiNx) may be formed on the gate lines 121 and thestorage electrode lines 131.

A plurality of semiconductor strips 151 preferably made of hydrogenatedamorphous silicon (abbreviated to “a-Si”) is formed on the gateinsulating layer 140. As illustratively shown, each semiconductor strip151 extends substantially in the longitudinal direction and has aplurality of projections 154 branched out toward the gate electrodes124. An extension 156 may be elongated from the projection 154.

Each of the semiconductor strips 151 is repeatedly bent and includes aplurality of pairs of oblique portions and a plurality of longitudinalportions. Two oblique portions making a pair are connected to each otherto form a chevron and opposite ends of the pair of oblique portions areconnected to respective longitudinal portions. In one embodiment, theoblique portions of the semiconductor strip make an angle about 45degrees with the gate lines 121, and the longitudinal portions crossover the gate electrodes 124. Illustratively, a pair of oblique portionsis about one to nine times longer than a longitudinal portion. That is,it occupies about 50-90 percent of the total length of the pair ofoblique portions and the longitudinal portion.

The extension 156 includes a drain portion extended obliquely from theprojection 154, a pair of oblique portions making an angle about 45degrees with the gate lines 121, and a connector connecting the drainportion and an end of the pair of oblique portions.

A plurality of ohmic contact strips 161 and islands 165, preferably madeof silicide or n+ hydrogenated a-Si heavily doped with n type impurity,may be formed on the semiconductor strips 151, extensions 156 andislands 154. Each ohmic contact strip 161 has a plurality of projections163. In one embodiment, the projections 163 and the ohmic contactislands 165 are located in pairs on the projections 154 of thesemiconductor strips 151.

The edge surfaces of the semiconductor strips 151 and the ohmic contacts161, 165, and 166 are tapered, and the inclination angles of the edgesurfaces of the semiconductor strips 151 and the ohmic contacts 161,165, and 166 are preferably in a range of about 30-80 degrees.

A plurality of data lines 171, a plurality of drain electrodes 175, anda plurality of coupling electrodes 176 are formed on the ohmic contacts161, 165, and 166 and the gate insulating layer 140, respectively.

Designed to transmit data voltages, the data lines 171 extendsubstantially in the longitudinal direction and intersect both the gatelines 121 and the storage electrode lines 131. Each data line 171 isbent repeatedly and includes a plurality of pairs of oblique portionsand a plurality of longitudinal portions. In one embodiment, each pairof oblique portions is connected to form a chevron. The opposite ends ofeach pair of oblique portions are connected to respective longitudinalportions. The oblique portions of the data lines 171 make an angle ofabout 45 degrees with the gate lines 121, and the longitudinal portionscross over the gate electrodes 124. The length of a pair of obliqueportions is about one to nine times the length of a longitudinalportion. That is, it occupies about 50-90 percent of the total length ofthe pair of oblique portions and the longitudinal portion. When an LCDis configured in this manner, pixel areas defined by crossing of thegate line 121 and the data line 171 appear to have a bent strip shape.

As shown in FIG. 1, each data line 171 may include a data pad 179 thatis wider than the data line for contacting another layer or an externaldevice. A plurality of branches of each data line 171 may project towarddrain electrodes 175 to form a plurality of source electrodes 173. Asshown, pairs of source electrodes 173 and drain electrodes 175 areseparated from each other and positioned on a gate electrode 124. In oneembodiment, the combination of a gate electrode 124, a source electrode173, and a drain electrode 175, together with a projection 154 of asemiconductor strip 151, forms a TFT having a channel formed in theprojection 154 disposed between the source electrode 173 and the drainelectrode 175.

A plurality of coupling electrodes 176 are formed on the same layer andmade of the same material as the drain electrode 175. The couplingelectrodes 176 are connected to the drain electrodes 175 and extend fromthe drain electrode 175. A first portion of a coupling electrode 176makes an angle of about 135 degrees with a gate line 121 and the secondportion of the coupling electrode 176 makes an angle of 45 degrees withthe gate line 121. The first and second portions of coupling electrode176 are substantially parallel corresponding oblique portions of thedata line 171.

As shown, the coupling electrode 176 may include an expansion connectorthat overlaps the storage electrode 133. The expansion of the couplingelectrode 176 increases storage capacitance and widens a contact areawith the first pixel electrode 190 a.

Each of data lines 171, the drain electrodes 175, and the couplingelectrodes 176 may have a multi-layered structure that includes twofilms having different physical characteristics. For example, each dataline drain electrode, and coupling electrode may include a lower film(not shown) and an upper film (not shown). In one embodiment, the upperfilm may be preferably made of low resistivity metal that includes, forexample, Al or an Al alloy. A low resistivity material is used to reducesignal delay or voltage drop in the data lines. On the other hand, thelower film may be preferably made of a material that has good contactcharacteristics with other materials such as indium tin oxide (ITO),indium zinc oxide (IZO) or similar materials. Illustrative lower filmmaterials include but are not limited to Cr, Mo, or a Mo alloy. A goodexemplary combination of the lower film material and the upper filmmaterial is Cr and Al—Nd alloy. In such a combination, Cr forms thelower material and an Al—Nd alloyforms the upper film.

Additionally, the lateral sides of each of the data lines 171, the drainelectrodes 175, and the coupling electrodes 176 may be tapered. Iftapered, the inclination angle of the lateral sides with respect to asurface of the substrate 110 is in the range of about 30-80 degrees.

A passivation layer 180 may be formed on the data lines 171, the drainelectrodes 175, and the coupling electrodes 176. In one embodiment, thepassivation layer 180 is preferably made of a flat photosensitiveorganic material and low dielectric insulating material having adielectric constant under 4.0. Exemplary materials used to formpassivation layer 180 include, but are not limited to a-Si:C:O anda-Si:O:F, each formed by plasma enhanced chemical vapor deposition(PECVD). Alternatively, an inorganic material such as silicon nitride,silicon oxide or similar material may be used.

In one embodiment, passivation layer 180 includes a plurality of contactholes 181 and 182 that expose the drain electrodes 175 and the expansionconnectors 179 of the data lines 171, respectively. Additionally, thepassivation layer 180 and the gate insulating layer 140 have a pluralityof contact holes 183 that expose the gate pads 129 of the gate lines121. Illustratively, the sidewalls of the contact holes 181, 182, and183 may make an angle of about 30-85 degrees with respect to the surfaceof the substrate 110 and may also include one or more stepped portions.Depending on the embodiment, the contact holes 181, 182, and 183 mayhave various planar shapes, such as a rectangular or circular shape. Inone embodiment, the area of each contact hole 181, 182, and 183 ispreferably greater than or equal to about 0.5 mm×15 μm and not largerthan about 2 mm×60 μm.

In one embodiment, a plurality of pairs of pixel electrodes 190 a and190 b and a plurality of contact assistants 81 and 82, which arepreferably made of ITO, IZO or Cr, are formed on the passivation layer180.

Referring to FIG. 14 and FIG. 17, a first pixel electrode 190 a and asecond pixel electrode 190 b are shown. In one embodiment, the firstpixel electrode 190 a has a bent band shape that follows the shape ofthe pixel area. Pixel electrode 190 a also includes a cutout 191. Thesecond pixel electrode 190 b includes two separated parallelograms. Asillustratively shown, the first pixel electrode 190 b may be disposedbetween the two parallelograms of the second pixel electrode 190 b. Inthis configuration, the first pixel electrode 190 b and the second pixelelectrode 190 b occupy substantially the same area.

The first pixel electrode 190 a physically and electrically connects tothe coupling electrodes 176 through the contact holes 181. The secondpixel electrode 190 b is physically and electrically floated, butoverlaps the coupling electrode 176 to form coupling capacitance withthe first pixel electrodes 190 a. Therefore, the voltage of the secondpixel electrode 190 b depends on the voltage of the first pixelelectrode 190 a. The voltage of the second pixel electrode 190 b withrespect to the common voltage is always smaller than that of the firstpixel electrode 190 a. Therefore, applied voltage at the center of apixel area is higher than that applied to both sides of a pixel area. Inthe present embodiment, the coupling electrode 176 play a role ofpassage for image signal from a thin film transistor to the first pixelelectrode 190 a as well as coupling of the first pixel electrode 190 aand the second pixel electrode 190 b. In the embodiment illustrated, thecoupling electrode 176 routes an image signal from a thin filmtransistor to the first pixel electrode 190 a. It also couples the firstpixel electrode 190 a tu to the second pixel electrode 190 b.

In one embodiment, it shows that when a pixel area includes twosub-areas with somewhat different electric fields, a mutual compensationin the two subareas improves the lateral visibility.

The common electrode panel 200 is now described with respect to FIGS.15, 16, and 17. Referring to FIG. 15, black matrix 220 for preventinglight leakage is formed on an insulating substrate 210 such astransparent glass. A plurality of red, green and blue color filters 230are formed on the black matrix and the substrate 210 and extendsubstantially along the columns of the pixel areas and are periodicallybent as the shape of the pixel areas bends. In other words, the colorfilters 230 extend substantially in the longitudinal direction alongpixel columns defined by black matrix 220 and are periodically bentalong the shape of pixels area. As shown in FIG. 4, an overcoat 250 isformed on the color filters 230 and the black matrix 220. A commonelectrode 270, preferably made of transparent conductive material suchas ITO and IZO, may be formed on the overcoat 250. In one embodiment,the common electrode 270 includes a plurality of cutouts 271 and 272.The cutouts 271 and 272 may function as domain control means and arepreferably about 9˜12 μm wide. When organic protrusions replace thecutouts 271, the organic protrusions are preferably about 5˜10 μm wide.As shown in FIG. 4, each pair of cutouts 271 and 272 are disposed in apixel area and is bent along the shape of pixel area. The cutouts 271and 272 are respectively disposed to divide the first pixel electrodes190 a and the second pixel electrode 190 b into right half portions andleft half portions. Both ends of the cutouts 271 and 272 are bent andextend to a predetermined length in a direction that substantiallyparallels the gate lines 121. Centers of the cutouts 271 and 272 alsoextend to a predetermined length and are substantially parallels thegate lines 121. In one embodiment, the extending direction of thecenters of the cutouts 271 and 272 is opposite to that of the ends ofthe cutouts 271 and 272.

Referring to FIG. 15, a cutout 271 of common electrode 270 may bedisposed in a pixel area and is bent along the shape of the pixel area.The cutout 271 may be disposed to divide the first pixel electrode 190 aand the second pixel electrode 190 b into right half portions and lefthalf portions. Both ends of the cutout 271 may be bent and extend to apredetermined length in a direction parallel with the gate line 121.Centers of the cutout 271 may also extend to a predetermined length andbe substantially parallel the gate line 121. As shown the extendingdirection of the center of the cutout 271 may be opposite to that of theends of the cutout 271. Additionally, the cutout 271 may also havebranches parallel the gate line 121 at points ¼ length and ¾ length asmeasured from one end of the cutout 271.

The LCD includes a TFT array panel 100, a color filter array panel 200facing the TFT array panel 100 and separated by a predetermined gap, anda liquid crystal layer 3 filled in the predetermined gap.

The LC molecules in the LC layer 3 are aligned such that their long axesare substantially vertical to the surfaces of the panels 100 and 200when there is no electric field. The liquid crystal layer 3 has negativedielectric anisotropy.

The thin film transistor array panel 100 and the color filter arraypanel 200 are assembled such that the pixel electrodes 190 a and 190 bprecisely correspond to the color filter 230. When the two panels 100and 200 are assembled, pixel areas are divided into a plurality ofsub-areas by the edge of the first and second pixel electrode 190 a and190 b and the cutouts 271 and 272. A liquid crystal region on eachsub-area is called a domain. Thus, in one embodiment, a pixel region isdivided into 4 domains by the cutouts 271 and 272. The domains have twoparallel longest edges. The distance between two longest edges of eachdomain, e.g., the width of the domain, is preferably about 10˜30 μm.

A pair of polarizers 12 and 22 is provided on the outer surfaces of thepanels 100 and 200, respectively, such that the transmissive axis ofeach polarizer is crossed. Additionally the pair of polarizers ispositioned so that at least one of the transmissive axes substantiallyparallels the gate lines 121.

The LCD may further include at least one retardation film (e.g., anoptical element that produces, for example, full, half, or quarter wavephase changes of polarized light). The retardation film functions tocompensate for the retardation of light caused by the LC layer 3.

In use, a common voltage is applied to the common electrode 270 and adata voltage is applied to the pixel electrodes 191 a and 191 b. Theapplication of these voltages generates a primary electric field whichis substantially perpendicular to the surfaces of the panels 100 and200. In response to the electric field, the LC molecules rotate untiltheir long axes are substantially perpendicular to the field direction.

The cutouts 271 and 272 of the common electrode 270 and the edges of thepixel electrodes 190 a and 190 b distort the primary electric field andgive it a horizontal component which determines the tilt directions ofthe LC molecules. The horizontal component of the primary electric fieldadopts four different orientations, thereby forming four domains in theLC layer 3 with different LC molecule tilt directions. The horizontalcomponent is substantially perpendicular to the first and second edgesof the cutouts 271 and 272, and substantially perpendicular to the edgeof the pixel electrode 190 a and 190 b. Accordingly, four domains havingdifferent tilt directions are formed in the LC layer 300. In analternative embodiment, a plurality of protrusions formed on the commonelectrode 270 may be substituted for the cutouts 271 and 272 because thetilt directions of the LC molecules also can be controlled by aplurality of protrusions (not shown).

The direction of a secondary electric field due to the voltagedifference between the pixel electrodes 190 a and 190 b is substantiallyperpendicular to each of the edges of the cutouts 271 and 272.Accordingly, the field direction of the secondary electric fieldcoincides with that of the horizontal component of the primary electricfield. Consequently, the secondary electric field between the pixelelectrodes 190 a and 190 b enhances the tilt directions of the LCmolecules.

Since the LCD performs inversion (i.e., inverting the polarity of anapplied voltage) such as dot inversion, column inversion, etc., asecondary electric field that enhances the tilt directions of the LCmolecules may be attained by supplying an adjacent pixel electrode witha data voltage having opposite polarity with respect to the commonvoltage. As a result, a direction of the secondary electric fieldgenerated between adjacent pixel electrodes is equivalent to thehorizontal component of the primary electric field generated between thecommon and pixel electrodes. Thus, a secondary electric field betweenthe adjacent pixel electrodes may be generated to enhance the stabilityof the domains.

In one embodiment, the tilt directions of all the domains form an angleof about 45 degrees with the gate lines 121, and the gate lines 121 areparallel to or perpendicular to the edges of the panels 100 and 200.Since a 45-degree intersection of the tilt directions and transmissiveaxes of the polarizers results in maximum transmittance, the polarizerscan be attached such that the transmissive axes of the polarizers areparallel or perpendicular to the edges of the panels 100 and 200,thereby reducing the production cost.

As described above, when two pixel electrodes 190 a and 190 b havingdifferent voltages are disposed in a pixel area, the distortion of thegamma curve decreases by compensation of the two pixel electrodes 190 aand 190 b. This results in improved viewing angle and quality ofpicture.

FIG. 18 is a top view of an LCD according to another embodiment of thepresent invention.

When the compared with the embodiment of FIGS. 14 to 17, the embodimentof FIG. 18 switched the first pixel electrode 190 a with the secondpixel electrode 190 b and changed the site of the expansion of thecoupling electrode 176. The site of the storage electrode line 131 ismoved downside. That is, the first pixel electrode 190 a has twoseparate portions. The second pixel electrode 190 b has bent band shapeand is disposed between the two portions of the first pixel electrode190 a. The coupling electrode 176 has two expansions to be respectivelyconnected with the two portions of the first pixel electrode 190 a.

The embodiments of FIGS. 14 to 17 and FIG. 18 show TFT array panelsmanufactured using four photo-mask processes. However, persons skilledin the art will understand that the embodiments shown in FIGS. 14, 17and FIG. 18 may be adapted to TFT array panels manufactured through fivephoto-mask processes.

In the above described embodiments, cutouts formed in the commonelectrode may function as domain control means. Alternatively, however,protrusions formed on the common electrode may replace the cutouts. Whenprotrusions are used as domain control means, the planar pattern of theprotrusions may be the same as that of the cutouts.

As described above, to improve lateral visibility and aperture ratio,the pixel areas are formed to have a bent band shape and each pixel areahas two separated pixel electrodes which are applied with differentvoltages from each other. Additionally, the bent band shape of the pixelarea increases the pixel area's degree of spatial dispersibility.However, the increased spatial dispersibility may create a broken imagewhen a small images such as individual alphanumerical characters aredisplayed. Embodiments for alleviating this problem are described withreference to FIGS. 19-22, as follow.

FIG. 19 is a top view of a thin film transistor array panel for a LCDaccording to another embodiment of the present invention. FIG. 20 is atop view of a common electrode panel for a LCD according to anotherembodiment of the present invention. FIG. 21 is a top view of an LCDaccording to the embodiment shown in FIGS. 19 and 20. FIG. 22 is asectional view of the LCD shown in FIG. 21 taken along the lineXXII-XXII′.

An LCD according to an embodiment of FIGS. 19 to 22 includes a TFT arraypanel 100, a common electrode panel 200, and a LC layer 3 interposedbetween the panels 100 and 200 and containing a plurality of LCmolecules aligned vertical to surfaces of the panels 100 and 200.

Referring to FIGS. 19, 21, and 22, the array panel 100 also includes aplurality of gate lines 121 and a plurality of storage electrode lines131 formed on an insulating substrate 110.

As shown, the gate lines 121 extend substantially in a transversedirection and are separated from each other and transmit gate signals.The gate line 121 also includes a plurality of gate electrodes 124 aswell as gate pads 129 for connecting to an external circuit.

Like the gate lines 121, each storage electrode line 131 extendssubstantially in the transverse direction. In one embodiment, a storageelectrode lines 131 substantially parallels a gate line 121.Additionally, each storage electrode line includes a plurality ofbranches that form a corresponding plurality of storage electrodes 133.In one embodiment, each storage electrode 133 includes a pair of obliqueportions that make an angle of about 45 degrees with the storage line131. Two oblique portions forming a pair make an angle about 90 degreeswith each other. In use, storage electrode lines 131 are supplied with apredetermined voltage, for example, a common voltage applied to a commonelectrode 270 formed on the other panel 200 of the LCD, as shown in FIG.4.

Each of the gate lines 121 and the storage electrode lines 131 may havea multi-layered structure that includes two films that have differentphysical characteristics from each other. Illustratively, each line mayinclude a lower film (not shown) and an upper film (not shown). Theupper film is preferably made of a low resistivity metal, such as, forexample Al, a metal containing AL, or an AL alloy. A low resistivitymetal is used to reduce signal delay or voltage drop in the gate lines121 and the storage electrode lines 131. On the other hand, the lowerfilm is preferably made of a material such as Cr, Mo, or a Mo alloy.However, any material that has good contact characteristics with othermaterials such as indium tin oxide (ITO), indium zinc oxide (IZO) orsimilar materials, may be used. One exemplary combination of the lowerfilm material and the upper film material is Cr and a Al—Nd alloy. Insuch a combination, CR may form the lower film and the Al—Nd alloy mayform the upper film.

Referring to FIG. 22, the lateral sides of the gate lines 121 and thestorage electrode lines 131 may be tapered. It tapered, the inclinationangle of the lateral sides with respect to a surface of the substrate110 is in a range of about 30-80 degrees.

Referring to FIG. 22, gate insulating layer 140 preferably made ofsilicon nitride (SiNx) may be formed on the gate lines 121 and thestorage electrode lines 131.

A plurality of semiconductor strips 151 preferably made of hydrogenatedamorphous silicon (abbreviated to “a-Si”) is formed on the gateinsulating layer 140. As illustratively shown, each semiconductor strip151 extends substantially in the longitudinal direction and has aplurality of projections 154 branched out toward the gate electrodes124. An extension 156 may be elongated from the projection 154.

As illustratively shown, each semiconductor strips 151 is bentrepeatedly and includes a plurality of pairs of oblique portions and aplurality of longitudinal portions. Two oblique portions make a pair.Two pairs of oblique portions are connected to each other to form adouble chevron and opposite ends of the double chevron portion areconnected to respective longitudinal portions. The oblique portions ofthe semiconductor strip make an angle about 45 degrees with the gatelines 121, and the longitudinal portions cross over the gate electrodes124. A double chevron portion is about one to nine times longer than alongitudinal portion. That is, it occupies about 50-90 percent of thetotal length of a double chevron portion and a longitudinal portion.

In one embodiment, the extension 156 includes a drain portion extendedobliquely from the projection 154, a pair of oblique portions making anangle about 45 degrees with the gate lines 121, and a connectorconnecting the drain portion and an end of the pair of oblique portions.

A plurality of ohmic contact strips 161 and islands 165, preferably madeof silicide or n+ hydrogenated a-Si heavily doped with n type impurity,may be formed on the semiconductor strips 151 and extensions 156. Eachohmic contact strip 161 has a plurality of projections 163. In oneembodiment, the projections 163 and the ohmic contact islands 165 arelocated in pairs on the projections 154 of the semiconductor strips 151.

The edge surfaces of the semiconductor strips 151 and the ohmic contacts161, 165, and 166 are tapered, and the inclination angles of the edgesurfaces of the semiconductor strips 151 and the ohmic contacts 161,165, and 166 are preferably in a range of about 30-80 degrees.

A plurality of data lines 171, a plurality of drain electrodes 175, anda plurality of coupling electrodes 176 are formed on the ohmic contacts161, 165, and 166 and the gate insulating layer 140, respectively.

Consequently, one or more pixel areas may be defined by FIGS. 19-22,such pixel areas may have a triple bent strip shape crossing of the gateline 121 and the data line 171.

In one embodiment, the data lines 171 for transmitting data voltagesextend substantially in the longitudinal direction and intersect thegate lines 121 and the storage electrode lines 131. Each data line 171is bent repeatedly and includes a plurality of pairs of oblique portionsand a plurality of longitudinal portions. Two adjacent oblique portionsmake a pair. Two pairs of oblique portions are connected to each otherto form a double chevron and opposite ends of the double chevron portionare connected to respective longitudinal portions. The oblique portionsof the data lines 171 make an angle of about 45 degrees with the gatelines 121, and the longitudinal portions cross over the gate electrodes124. The length of a double chevron portion is about one to nine timesthe length of a longitudinal portion, that is, it occupies about 50-90percent of the total length of a double chevron portion and alongitudinal portion.

As shown in FIG. 19, each data line 171 may include a data pad 179 thatis wider than the data line for contacting another layer or an externaldevice. A plurality of branches of each data line 171 may project towarddrain electrodes 175 to form a plurality of source electrodes 173. Asshown, pairs of source electrodes 173 and drain electrodes 175 areseparated from and facing each other with a gate electrode 124 therebetween. In one embodiment, the combination of a gate electrode 124, asource electrode 173, and a drain electrode 175, together with aprojection 154 of a semiconductor strip 151, forms a TFT having achannel formed in the projection 154, disposed between the sourceelectrode 173 and the drain electrode 175.

As shown in FIGS. 19-22, a plurality of coupling electrodes 176 areformed on the same layer and made of the same material as the drainelectrode 175. Coupling electrodes 176 are connected to the drainelectrodes 175 extended from the drain electrode 175. A first portion ofthe coupling electrode 176 makes an angle of 135 degrees with a gateline 121. A second portion of the coupling electrode 176 makes an angleof about 45 degrees with the gate line 121. The first and secondportions of coupling electrode 176 are substantially parallel with thedouble chevron portions of the data line 171. Thus in one embodiment,the coupling electrode 176 may also have a double chevron shape.

As shown, the coupling electrodes 176 have an expansion that overlapsthe storage electrode 133. The expansion of the coupling electrode 176increases storage capacitance and widens a contact area with a firstpixel electrode 190 a.

Each of data lines 171, the drain electrodes 175, and the couplingelectrodes 176 may have a multi-layered structure that includes twofilms having different physical characteristics. For example, each dataline drain electrode, and coupling electrode may include a lower film(not shown) and an upper film (not shown). In one embodiment, the upperfilm may be preferably made of low resistivity metal that includes, forexample, Al or an Al alloy. A low resistivity material is used to reducesignal delay or voltage drop in the data lines. On the other hand, thelower film may be preferably made of a material that has good contactcharacteristics with indium tin oxide (ITO), indium zinc oxide (IZO) orsimilar materials. Illustrative lower film materials include but are notlimited to Cr, Mo, or a Mo alloy. A good exemplary combination of thelower film material and the upper film material is Cr and Al—Nd alloy.In such a combination, Cr forms the lower material and an Al—Ndalloyforms the upper film.

Additionally, the lateral sides of each of the data lines 171, the drainelectrodes 175, and the coupling electrodes 176 may be tapered. Iftapered, the inclination angle of the lateral sides with respect to asurface of the substrate 110 is in the range of about 30-80 degrees.

A passivation layer 180 may be formed on the data lines 171, the drainelectrodes 175, and the coupling electrodes 176. In one embodiment, thepassivation layer 180 is preferably made of a flat photosensitiveorganic material and low dielectric insulating material having adielectric constant under 4.0. Exemplary materials used to formpassivation layer 180 include, but are not limited to a-Si:C:O anda-Si:O:F, each formed by plasma enhanced chemical vapor deposition(PECVD). Alternatively, an inorganic material such as silicon nitride,silicon oxide or other similar material may be used.

In one embodiment, passivation layer 180 includes a plurality of contactholes 181 and 182 that expose the drain electrodes 175 and the expansionconnectors 179 of the data lines 171, respectively. Additionally, thepassivation layer 180 and the gate insulating layer 140 have a pluralityof contact holes 183 that expose the expansion connectors 129 of thegate lines 121. Illustratively, the sidewalls of the contact holes 181,182, and 183 may make an angle of about 30-85 degrees with respect tothe surface of the substrate 110 and may also include one or morestepped portions. Depending on the embodiment, the contact holes 181,182, and 183 may have various planar shapes, such as a rectangular orcircular shape. In one embodiment, the area of each contact hole 181,182, and 183 is preferably greater than or equal to about 0.5 mm×15 μmand not larger than about 2 mm×60 μm.

In one embodiment, a plurality of pairs of pixel electrodes 190 a and190 b and a plurality of contact assistants 81 and 82, which arepreferably made of ITO, IZO or Cr, are formed on the passivation layer180.

As previously described, the first pixel electrode 190 a and the secondpixel electrode 190 b may respectively occupy a lower half and upperhalf of a pixel area defined by the crossing of two gate lines 121 andtwo data lines 171. Illustratively, each of the first pixel electrode190 a and the second pixel electrode 190 b may have a shape of singlebent band. Additionally, the first pixel electrode 190 b may have atransverse cutout 191, and the second pixel electrode 190 b may have atransverse cutout 192.

In one embodiment, the first pixel electrode 190 a physically andelectrically connects to the coupling electrodes 176 through the contactholes 181. The second pixel electrode 190 b is physically andelectrically floated, but overlaps with the coupling electrode 176 toform coupling capacitances with the first pixel electrode 190 a.Therefore, the voltage of the second pixel electrode 190 b depends onthe voltage of the first pixel electrode 190 a. Consequently, thevoltage of the second pixel electrode 190 b with respect to the commonvoltage will always be smaller than that of the first pixel electrode190 a. As a result, applied voltage at lower half of a pixel area willbe higher than that at a upper half of the pixel area.

In the present embodiment, the coupling electrodes 176 routes an imagesignal from a thin film transistor to the first pixel electrode 190 aand couples the first pixel electrode 190 a, to the second pixelelectrode 190 b. As mentioned previously, lateral visibility is improvedby mutual compensation when a pixel area includes two sub-areas thateach have somewhat different electric fields. More significantly, theimproved spatial dispersibility of a pixel area achieved by embodimentsof the invention prevents broken images even in a LCD that has low pixeldensity.

A plurality of contact assistants 81 and 82 may be respectivelyconnected to the gate pads 129 of the gate lines 121 and the gate pads179 of the data lines 171 through the contact holes 182 b and 183 bformed on the passivation layer 180. The pixel electrodes 190 a and 190b and the contact assistants 81 and 82 may be made of ITO (indium tinoxide), IZO (indium zinc oxide), or similar materials.

The common electrode panel 200 will be described with respect to FIGS.20, 21, and 22.

A plurality of red, green and blue color filters 230 are formed on theblack matrix and the substrate 210 and extend substantially along thecolumns of the pixel areas and periodically bend as the shape of thepixel areas bends. In other words, the color filters 230 extendsubstantially in the longitudinal direction along pixel columns definedby black matrix 220 and are periodically bent along the shape of pixelsarea. A common electrode 270, preferably made of transparent conductivematerial such as ITO and IZO may be formed on the color filter 230. Inone embodiment, the common electrode 270 includes a plurality of cutouts271 and 272. The cutouts 271 and 272 may function as domain controlmeans and preferably have width of about 9˜12 μm. When organicprotrusions replace the cutouts 271, the organic protrusions preferablyhave width of 5˜10 μm.

Referring to FIG. 20, a cutout 271 of common electrode 270 is disposedin a pixel area and bent along the shape of a pixel area. The cutout 271is disposed to divide the first pixel electrode 190 a and the secondpixel electrode 190 b into right half portions and left half portions.Both ends of the cutout 271 are bent and extended to a predeterminedlength in a direction parallel with the gate line 121. The first andthird bent portion also extended a predetermined length in a directionsubstantially parallel with the gate line 121 but opposite to the endsof the cutout 271. The second bent portion extended to a predeterminedlength in a direction of the same with the ends of the cutout 271.

As shown, the LCD may include a TFT array panel 100, a color filterarray panel 200 facing the TFT array panel 100 and separated by apredetermined gap, and a liquid crystal layer 3 filled in thepredetermined gap.

The LC molecules in the LC layer 3 are aligned such that their long axesare substantially vertical to the surfaces of the panels 100 and 200when there is no electric field. The liquid crystal layer 3 has negativedielectric anisotropy.

The thin film transistor array panel 100 and the color filter arraypanel 200 are assembled such that the pixel electrodes 190 a and 190 bprecisely correspond to the color filter 230. When the two panels 100and 200 are assembled, pixel areas are divided into a plurality ofsub-areas by the edge of the first and second pixel electrode 190 a and190 b and the cutouts 271 and 272. A liquid crystal region on eachsub-area is called a domain. Thus, in one embodiment, a pixel region isdivided into 4 domains by the cutouts 271 and 272. The domains have twoparallel longest edges. The distance between two longest edges of eachdomain, e.g., the width of the domain, is preferably about 10˜30 μm.

A pair of polarizers 12 and 22 is provided on the outer surfaces of thepanels 100 and 200, respectively, such that the transmissive axis ofeach polarizer is crossed. Additionally the pair of polarizers ispositioned so that at least one of the transmissive axes substantiallyparallels the gate lines 121.

The LCD may further include at least one retardation film (e.g., anoptical element that produces, for example, full, half, or quarter wavephase changes of polarized light). The retardation film functions tocompensate for the retardation of light caused by the LC layer 3.

In use a common voltage is applied to the common electrode 270 and adata voltage is applied to the pixel electrodes 191 a and 191 b. Theapplication of their voltages generates a primary electric field whichis substantially perpendicular to the surfaces of the panels 100 and200. In response to the electric field, the LC molecules rotate untiltheir long axes are perpendicular to the field direction. The cutouts271 and 272 of the common electrode 270 and the edges of the pixelelectrodes 190 a and 190 b distort the primary electric field and giveit a horizontal component which determines the tilt directions of the LCmolecules. The horizontal component of the primary electric field adoptsfour different orientations, thereby forming four domains in the LClayer 3 with different LC molecule tilt directions. The horizontalcomponent is substantially perpendicular to the first and second edgesof the cutouts 271 and 272, and substantially perpendicular to the edgeof the pixel electrode 190 a and 190 b. Accordingly, four domains havingdifferent tilt directions are formed in the LC layer 300. In analternative embodiment, a plurality of protrusions formed on the commonelectrode 270 may be substituted for the cutouts 271 and 272 because thetilt directions of the LC molecules also can be controlled by aplurality of protrusions (not shown).

The direction of a secondary electric field due to the voltagedifference between the pixel electrodes 190 a and 190 b is substantiallyperpendicular to each of the edges of the cutouts 271 and 272.Accordingly, the field direction of the secondary electric fieldcoincides with that of the horizontal component of the primary electricfield. Consequently, the secondary electric field between the pixelelectrodes 190 a and 190 b enhances the tilt directions of the LCmolecules.

Since the LCD performs inversion (i.e., inverting the polarity of anapplied voltage) such as dot inversion, column inversion, etc., asecondary electric field that enhances the tilt directions of the LCmolecules may be attained by supplying an adjacent pixel electrode witha data voltage having opposite polarity with respect to the commonvoltage. As a result, a direction of the secondary electric fieldgenerated between adjacent pixel electrodes is equivalent to thehorizontal component of the primary electric field generated between thecommon and pixel electrodes. Thus, a secondary electric field betweenthe adjacent pixel electrodes may be generated to enhance the stabilityof the domains.

In one embodiment, the tilt directions of all the domains form an angleof about 45 degrees with the gate lines 121, and the gate lines 121 areparallel to or perpendicular to the edges of the panels 100 and 200.Since a 45-degree intersection of the tilt directions and transmissiveaxes of the polarizers results in maximum transmittance, the polarizerscan be attached such that the transmissive axes of the polarizers areparallel or perpendicular to the edges of the panels 100 and 200,thereby reducing the production cost.

As described above, when two pixel electrodes 190 a and 190 b havingdifferent voltages are disposed in a pixel area, the distortion of thegamma curve decreases due to compensation created by the two pixelelectrodes 190 a and 190 b. Furthermore, since the spatialdispersibility of a pixel area is diminished, broken image is preventedeven in an LCD that has a low density of pixels.

FIG. 23 is a top view of a thin film transistor array panel for a LCDaccording to another embodiment of the present invention. FIG. 24 is atop view of a common electrode panel for a LCD according to anotherembodiment of the present invention. FIG. 25 is a top view of an LCDaccording to the embodiment shown in FIGS. 23 and 24.

When compared with the embodiment of FIGS. 19 to 22, the embodiment ofFIGS. 23, 24 and 25 reduced the size of first pixel electrode 190 a byabout a ¼ and increased the size of the second pixel electrode 190 b byabout a ¼. As shown, the cutouts 271 of the common electrode 270 furtherinclude branch cutouts which overlap the boundary area of the first andsecond pixel electrodes 190 a and 190 b.

In one embodiment, a ratio of the first pixel electrode 190 a and thesecond pixel electrode 190 b may be altered according to the propertiesdesired in a LCD.

In the embodiment of FIGS. 23 to 25, the pixel areas are formed to havea triple bent band shape and are divided into upper and lower portionsby the first pixel electrode 190 a and the second pixel electrode 190 b.However, even though pixel areas have triple bent band shape, the firstand second pixel electrodes 190 a and 190 b may be formed to divide thepixel areas into left and right portions.

The embodiments of FIGS. 23 to 25 show TFT array panels manufacturedusing four photo-mask processes. However, it will be easy to understandto those skilled in the art that the ideas of the embodiments of FIGS.23 to 25 may be adapted to TFT array panels manufactured using fivephoto-mask processes.

In the above described embodiments, cutouts formed in the commonelectrode are shown as domain control means. However, protrusions formedon the common electrode may replace the cutouts. When protrusions areused as domain control means, the planar pattern of the organicprotrusions may be the same as that of the cutouts.

In the above described embodiments, the color filters are formed on thecommon electrode panel. However, the color filters may be formed on theTFT array panel, more concretely between the passivation layer and thepixel electrodes.

As described above, when a pixel areas are formed to have a bent bandshape, a secondary electric field between the adjacent pixel electrodescan be generated to enhance the stability of the domains and thepolarizers can be attached such that the transmissive axes of thepolarizers are parallel or perpendicular to the edges of the panels 100and 200, thereby reducing the production cost.

An LCD according to the present invention includes several sub-areaswith somewhat different electric fields, and lateral visibility isimproved by the mutual compensation of the sub-areas.

The embodiments of FIGS. 19 to 22 and FIGS. 23 to 25 show pixel shapesof triple vent band. However, the invention is not limited to a triplebent band shape, but includes other multiple bent band shapes. Such amulti-vent band shape is helpful to reduce spatial dispersibility of apixel area. Reduction of spatial dispersibility of a pixel area ishelpful to prevent a character from being seen as broken.

While the present invention has been described in detail with referenceto the preferred embodiments, those skilled in the art will appreciatethat various modifications and substitutions can be made thereto withoutdeparting from the spirit and scope of the present invention as setforth in the appended claims.

1. A flat panel display, comprising: a first panel; a second panel; and a liquid crystal layer interposed between the first panel and the second panel, wherein the first panel comprises: a substrate having a plurality of pixel areas, each pixel area including a first sub-pixel area and a second sub-pixel area, the first sub-pixel area configured to have a greater electric field than the second sub-pixel area, such that mutual compensation in the two sub-pixel areas decreases distortion of a gamma curve and improves lateral visibility of the flat panel display; a plurality of gate lines; a data line comprising longitudinal portions perpendicularly crossing over the gate lines, and at least one bent portion disposed between the longitudinal portions; a thin film transistor (TFT) formed on the substrate and comprising a gate electrode, a source electrode connected to the data line and a drain electrode; a coupling electrode electrically connected to the drain electrode; a first sub-pixel electrode formed in the first sub-pixel area and connected to the drain electrode; and a second sub-pixel electrode formed in the second sub-pixel area, floated and overlapping the coupling electrode to form coupling capacitances with the first sub-pixel electrode, wherein at least one of the first sub-pixel electrode and the second sub-pixel electrode have a shape of a bent-band that matches the shape of the pixel areas, and the second panel comprises a common electrode having at least one cutout or at least one protrusion, the at least one cutout or at least one protrusion dividing the pixel area into a plurality of sub-areas.
 2. The flat panel display of claim 1, wherein the cutout or the protrusion is bent along a shape of the pixel area.
 3. The flat panel display of claim 2, wherein the cutout or the protrusion comprises: a plurality of oblique portions, the oblique portions being connected to form a chevron; and a first extension extended from ends of the oblique portions.
 4. The flat panel display of claim 3, further comprising a second extension extended from a position where the oblique portions are connected.
 5. The flat panel display of claim 3, wherein the data line comprises a plurality of oblique portions disposed between the longitudinal portions, and the oblique portions make an angle of about 45 degrees with the gate lines, and the oblique portions of the cutout or the protrusion are parallel to the oblique portions of the data line.
 6. The flat panel display of claim 5, further comprising a pair of polarizers disposed on outer surfaces of the first and the second panels, wherein transmission axes of the polarizers are crossed with each other, and the pair of polarizers is disposed so that at least one of the transmission axes parallels the gate lines.
 7. The flat panel display of claim 2, further comprising a storage electrode line and a storage electrode connected to the storage electrode line and overlapping the first sub-pixel electrode.
 8. The flat panel display of claim 7, wherein at least a portion of the storage electrode is extended along the at least one cutout or at least one protrusion.
 9. The flat panel display of claim 7, wherein the cutout or the protrusion comprises: a plurality of oblique portions, the oblique portions being connected to form a chevron; and a first extension extended from ends of the oblique portions.
 10. The flat panel display of claim 9, further comprising a second extension extended from a position where the oblique portions are connected.
 11. The flat panel display of claim 9, wherein the data line comprises a plurality of oblique portions disposed between the longitudinal portions, and the oblique portions make an angle of about 45 degrees with the gate lines, and the oblique portions of the cutout or the protrusion are parallel to the oblique portions of the data line.
 12. The flat panel display of claim 11, further comprising a pair of polarizers disposed on outer surfaces of the first and the second panels, wherein transmission axes of the polarizers are crossed with each other, and the pair of polarizers is disposed so that at least one of the transmission axes parallels the gate lines. 